A vehicle monitoring apparatus is known, including a camera that is mounted on a vehicle and includes a wide-angle lens for capturing an area surrounding the vehicle in a wide field of view; an image extraction means for extracting an image from a predetermined region of the image captured by the camera via the wide-angle lens; a display means for displaying the image extracted by the image extraction means; and an obstacle detecting means for detecting an obstacle in the area surrounding the vehicle. The vehicle monitoring apparatus extracts from the video image an image corresponding to the direction in which the obstacle detected by the obstacle detecting means is located and displays an enlarged view of that image on a display unit (see, for example, Patent Document 1). In further detail, under normal conditions, an entire image captured by the camera, an image extracted from the lower center of the video image, an image extracted from the lower right of the video image, and an image extracted from the lower left of the video image are displayed repeatedly and sequentially for a predetermined period of time. If an obstacle is detected by the right rear sonar, from the video image stored in the image memory, a predetermined left-side region of the image is extracted and displayed as an enlarged view in full screen mode (as the camera is pointed rearward from the vehicle, the obstacle, located rear right of the vehicle is on the left side of the video image). If an obstacle is detected by the left rear sonar, a predetermined right-side region of the image is extracted from the video image and displayed as an enlarged view in full screen mode. It is also proposed to provide a small auxiliary screen in a predetermined position on the display screen (for example, in the upper right on the screen) to display the position of the vehicle and the image capture area corresponding to the extracted image. According to this vehicle monitoring apparatus, however, since the part of the monitor display video image that shows a detected obstacle is extracted and displayed in an enlarged view, no image of the obstacle can be displayed if the obstacle is not in the video image displayed on the monitor. If the image capture field of view is widened to avoid this problem, the image region in the center of the field of view which serves an important purpose under normal conditions, becomes relatively small with respect to the display area of the monitor, making it difficult to confirm the condition of the surrounding area through the image displayed on the monitor.
A vehicle surrounding-area monitoring apparatus is known from Patent Document 2 that generates, based on obstacle distance and obstacle condition information regarding a detected obstacle, a single obstacle display image showing both obstacle distance and obstacle condition information and generates image signals for showing a video sequence of the generated obstacle images. In this apparatus, when an obstacle(s) approaches the vehicle from one or both sides of the vehicle, the monitor screen displays an image generated by using mapping to enlarge the surrounding areas that correspond to both sides of the vehicle as well as an obstacle display image in which a vehicle icon and an obstacle icon are arranged. Here, the obstacle icon is configured to indicate the obstacle distance, the direction of approach, the speed of approach, and the time of arrival of the obstacle by its position in relation to the vehicle icon, shape, size, and color. With the help of the video image enlarging both sides of the vehicle and the obstacle display image, obstacles approaching from either side of the vehicle can be recognized more easily. However, the displayed video image is acutely distorted in order to enlarge the surrounding areas corresponding to both sides of the vehicle, resulting in a distorted center region and a generally difficult image to view. Furthermore, since the video image itself is a wide view-field image, even the acute partial enlargement still produces outer obstacle images of limited size. Furthermore, the use of icons in the periphery (in the lower portion) of video images to indicate the locations and approaching of obstacles necessitates combination of completely different types of image information, i.e., the video images of actual scenery and abstract images, such as icons, which is not conducive to intuitive recognition of obstacles.
The vehicle surrounding-area monitoring apparatus described in Patent Document 3 generates a narrow view-field image showing part of the area surrounding the vehicle from the image of the area surrounding the vehicle obtained by an imaging unit and, if the obstacle recognized in the area surrounding the vehicle is not contained in the narrow view-field image, the region of the image containing the obstacle is cut out from the video image as an obstacle image and output to the monitor with the narrow view-field image. The narrow view-field image and the obstacle image, displayed if an obstacle is recognized around the vehicle, have a uniform image quality since they are both cut out from the same video image. However, no continuity exists between the narrow view-field image and the obstacle image as they are independently cut out from the video image, thus making it difficult to recognize the positional relationship therebetween.